1. Field of the Invention
This invention relates to instruments for use in surgery and in particular, instruments for use in knee replacement surgery for preparation of bone tissue for receipt of joint prosthesis.
2. Background
It has long been known that implants may be devised which can be used to replace the natural joints provided in the mamillian body. In particular knee and hip replacements in humans is becoming more common. As these operations become more common, the need to replace worn out, old implants with newer or stronger implants or to readdress a progressive bone disease is on the upswing.
When performing, for example, knee revision surgery, a substantial portion of the bone at the distal end of the femoral bone and the proximal end of the tibial bone is removed. The removed bone makes way for the portion taken up by the new implant which is inserted into and fixed to the bone. This fixed implant is then received within the body to act as a replacement for the removed bone tissue.
Occasionally, it becomes necessary to replace a previously implanted prosthesis with a new prosthesis. In performing the replacement or revision surgery, it is necessary to remove the old prosthesis, either due to the continued disease of the bone or failure of the prosthesis itself.
In revision surgery, that is surgery where a new prosthesis is being implanted in the place of an old prosthesis, a substantial additional quantity of bone is removed. Often the removal of the implant itself destroys much of the bone tissue which surrounds the mounting site of the implant or the disease has advanced to such a state as to require a large amount of bone removal, both internal to the bone itself and along the distal or proximal portions as the case may be.
In performing this revision type of surgery, the removal of the old prosthesis and the large volume which is devoid of supporting bone attendant with the implant removal, creates a situation where it is difficult to provide sufficient mounting for the instruments necessary to make the accurate cuts needed for the new implant. That is, there is not a sufficient anchor site to provide positioning for the instrumentation in order to make accurate and complete cuts.